1.1 Introduction to the Cell Theory

Question 1

All living things are made of cells

Answer 1

Unicellular organisms: single-celled

Multicellular organisms: specialised cells, carry out specific functions

Question 2

Cells are the smallest units of life

Answer 2

Organelles are not living; they are specialised structures within cells that carry out different functions

Question 3

Cells come from pre-existing cells

Answer 3

Cells multiply through division
Mitosis: genetically identical diploid daughter cells
Meiosis: generates haploid gametes (sex cells)

Question 4

Limitations/exceptions to the cell theory

Answer 4

Striated muscle: 
- 300mm+ 
- very long
-multi-nucleated 
Giant algae: 
- up to 100mm
- unicellular 
- one nucleus 
Fungal hyphae:
- continuous cytoplasm 
- multi-nucleated 
- chitin cell wall (not cellulose)

Question 5

Characteristics of living organisms

Answer 5

Mr H Gren

Metabolism
Respiration 
Stability/homeostasis
Growth 
Response 
Excretion 
Nutrition

Question 6

Metabolism

Answer 6

The body’s ability to have chemical process carried out by the cell

Question 7

Reproduction

Answer 7

Production of offspring
Mitosis: creates 2 genetically identical diploid cells
Meiosis: generates 4 haploid gametes (sex cells)

Question 8

Homeostasis

Answer 8

Maintaining internal conditions/ keeping it constant + safe

Question 9

Growth

Answer 9

Increase in size (cell size or number of cells)

Question 10

Response

Answer 10

Ability to react to depending on external factors /environment

Question 11

Excretion

Answer 11

Removement of waste as a result of metabolism

Question 12

Nutrition

Answer 12

Ability to get food in order to produce energy and gather substances needed for growth

Question 13

Calculating magnification and actual size

Answer 13

Magnification = measured length/bar label

Actual size = image length/magnification

make sure units are constant

Question 14

Paramecium vs. Chlamydomonas (functions of life)

Answer 14

Metabolism: produce enzymes that catalyze chemical reactions
Reproduction: reproduce sexually and asexually
Homeostasis: keeps internal conditions constant - e.g. Expels excess water using contractile vacuole
Growth: food vs. photosynthesis
Excretion: co2 from respiration vs. oxygen from photosynthesis
Nutrition: feeds on smaller organisms vs. creates own food

Question 15

Multicellular organisms

Answer 15

Made of multiple cells

Cells differentiate to create specialise tissues (groups of cells) that carry out different functions

Question 16

State the cell theory

Answer 16

All living things are made of cells
Cells are the smallest units of life
Cells come from pre-existing cells

Question 17

Emergent properties

Answer 17

Multicellular organisms have properties that emerge from the interaction of their cellular components.
“The whole is greater than the sum of its parts”
e.g. bone, muscle and tendon (muscular system)
when the muscle contracts, it pulls on the tendon which causing the tendon to pull on the bone
without the muscle and tendon working with the bone, the bone would have no movement

Question 18

Stem cells

Answer 18

Stem cells are cells that are not yet differentiated. Stem cells retain the capacity to divide and have the ability to differentiate along different pathways.

2 types
- Pluripotent: adult stem cells; for repair and regeneration
Can differentiate into a range of different cells (but not all cells), adult tissues
E.g. bone marrow - not able to differentiate as kidney cells - but can differentiate into a multitude of white blood cells and red blood cells

• Totipotent: embryonic stem cells
  Can differentiate into any type of cell in the organism; all future cells stem from these

Question 19

Therapeutic stem cell use (Stargardt’s)

Answer 19

Stargart’s macular dystrophy: genetic disease that develops in children between 6-12; mostly due to a recessive mutation of a gene - causes membrane protein used for active transport in retina cells to malfunction so photoreceptive cells degenerate and vision becomes progressively worse

Researchers have developed methods to make EMBRYONIC STEM CELLS develop into retina cells
Cells are injected into the eyes

(still doing trials)

Question 20

Therapeutic stem cell use (Leukemia)

Answer 20

Leukemia: cancer in which abnormally large numbers of white blood cells are produced in the bone marrow

ADULT STEM CELLS are used in the treatment

• Fluid is removed from the bone marrow
• Stem cells are extracted from this fluid and are stored - adult stem cells and only have the potential for producing blood cells
• High dose of chemotherapy drug to kill all the cancer cells in the bone marrow - bone marrow loses its ability to produce blood cells
• Stem cells are returned to the patients body and re-establish themselves, multiply and start to produce red and white blood cells

Question 21

Ethics of therapeutic use of stem cells

Answer 21

• health and quality of life of patients suffering from otherwise incurable conditions may improve
• controversy on if an embryo is a form of human life or not

Question 22

Differentiation

Answer 22

Multicellular organisms have this ability
All have the same genome but different genes are activated depending on their function ~ follows a pathway
Once a cell follows a pathway, they can not follow another one -> “committed”

Question 23

SA: volume ratio

Answer 23

As the cell increases, the SA:volume ratio decreases
e.g. 
square - 1x1
SA = 6
Volume = 1
6:1 = 6

square 10x10
SA = 600
Volume = 1000
600:1000 - 0.06

• cells need to exchange substances - such as food, waste, heat, and gases
• cytoplasm, chemical reactions take place (metabolic reactions) -> reactions produce heat, wastes, and also consume resources
• rate of reactions is proportional to the volume of the cell
• exchange of materials and heat energy is a function of the cell’s surface area
• as cell size increases, SA:volume ratio decreases
• as SA:volume ratio decreases, the rate of exchange decreases.
• if metabolism is to continue at an optimum rate, substances (e.g. oxygen) must be absorbed and waste products such as (CO2) need to be removed
• if too much heat is produced during metabolism in comparison to the amount the cell is able to remove, the cell might overheat
• therefore, greater SA:volume ratio = faster the cell can remove waste and heat, and absorb oxygen and nutrients essential for the cell to function properly